Host requirements for growth of lambda-P22 hybrid in Escherichia coli
Journal of Bacteriology
The requirements for growth of bacteriophage X containing the deoxyribonucleic acid replication region from Salmonella phage P22 were determined in a burst size experiment. The products of genes dnaE, dnaJ, dnaK, dnaY, dnaZ, and seg were required, but not the products of genes dnaA, dnaB, dnaC, and dnaX. This X-P22 hybrid phage was also dependent onpolA for growth at 320C. The temperate phages P22 from Salmonella typhimurium and X from Escherichia coli share a common genetic organization.
... organization. Analogous genes coding for integration, recombination, control and immunity, DNA synthesis, and lysis functions are in corresponding positions in the genetic maps of both phages (2). Thus, the two phages are part of the same "lambdoid" family. Under the right conditions these two phages can forn viable hybrids with sections of P22 DNA substituting for X genes (3). Using these X-P22 hybrids, Hilliker and Botstein (7) demonstrated that the X DNA replication genes 0 and P singly are not capable of providing replication functions for P22 DNA and vice versa, but the entire replication regions of these phages can be exchanged as a unit between them. Since the hybrid phage carrying the P22 DNA replication region are viable in E. coli, the gene 18 and 12 proteins are capable of interaction with various E. coli proteins in a replication complex. The dnaB, dnaE, dnaG, dnaJ, dnaK, dnaY, dnaZ, grpD, grpE, and seg gene products, DNA ligase, and RNA polymerase are known to participate in A DNA replication (15) . Further, the AP protein is known to interact with the dnaB protein (5, 8, 16) and also with dnaJ, dnaK, grpD, and grpE (4,10, 13). By analogy to lambda, these proteins would be expected to be involved in DNA replication of the X-P22 hybrids, with the gene 12 protein functioning in a complex with dnaB, dnaJ, dnaK, grpD, and E. For this reason, we decided to investigate the gene requirements for P22 growth in E. coli. During preparation of this manuscript, we learned that Schanda-Mulfinger and Schmieger (11) made a similar report. We have confirmed their observation that X-P22 hybrid phage could be grown at 420C in E. coli carrying mutations in dnaA, dnaB, and dnaC, and that E. coli carrying mutations in dnaE, dnaK, and dnaZ could not support the growth of the hybrid P22 phage at 420C. We report here additional re-quirements of E. coli genes for growth of a A-P22 hybrid phage P22. The E. coli strains employed in this report are shown in Table 1 . The A-p22 hybrid phage [A (18, 12)'] employed in this report has a substitution of AO and P genes with P22 18 and 12 genes. The burst size of the hybrid phage in various dna mutants was measured at 32 and 420C by a single cycle of infection (Table 2) . Generally, the burst size of A (18, 12)P22 in all of the E. coli tested was much lower than that of A (0, P)x. A (18, 12)m requires the E. coli proteins of the dnaE, dnaJ, dnaK, dnaY, dnaZ, and seg genes, whereas the products of dnaA, dnaB, dnaC, and dnaX are not essential for the growth of the hybrid phage. Since A (18, 12)P'22 grew very poorly in both the dnaG(Ts) strain and its temperature-resistant revertant, we were unable to determine its requirement. As described by Schanda-Mulfinger and Schmieger (11) and confirned by us, A (18, 12)m could normally grow in a dnaB(Ts) mutant at both 32 and 420C. The other significant observation from the experiment is that A (18, 12)P' phage is dependent on the polA gene for its growth at 320C. This notion was confirmed by an efficiency of plating experiment on the poLAl mutant at 320C (Table 3) . On the P3478 strain, X (18, 12)m made very tiny plaques at 320C, whereas the phage formed much bigger plaques on its polAU revertant (PR3478) at the same temperature. On strain D110, the phage formed no plaques at 320C (the efficiency of plating was less than 10-6). The smaller plaque size observed with strain P3478 and the low efficiency of plating on D110 reflect the facts that P3478 contains 0.6% of the polymerase activity of the wild type (W3110) and that the level of residual polymerase inpoLAl mutants varies when this mutation is introduced into different genetic backgrounds (9) . The defect in plaque formation was cancelled by raising the incubation temperature to 1113 on May 9, 2020 by guest